1. Field of the Invention
The present invention relates to an exhaust control valve for controlling the flow of exhaust gas, and more particularly to an exhaust control valve for a motor vehicle exhaust gas system.
2. Background Art
In an exhaust control valve according to the background art as shown in Japanese Pre-examination Patent Publication (KOKAI) No. 63-212728 (1988), a cast valve having a crank-like shape has the flow of exhaust gas controlled by a crank portion.
However, this crank-like valve body suffers from some disadvantages. Since the shape of the valve body is asymmetrical with respect to the axis line of the valve shaft, distribution of melt is often defective at the time of casting from an end of the valve shaft, and thermal deformation due to partial material thickness can easily occur. In addition, since the crank portion serving as a valve portion makes contact with the valve housing over a small area, it is difficult to maintain high sealing properties. Further, since the weight balance about the axis line of the valve body is offset/poor, response to driving torque is relatively poor.
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
An aspect of the present invention is to provide an exhaust control valve which solves the afore-mentioned drawbacks of the background art, specifically to provide high sealing properties, improve thermal properties through improved casting integrity, and desirable weight distribution.
These and other aspects of the present invention are accomplished by an exhaust control valve comprising a valve housing having a valve chamber; a valve body having a cylindrical shape rotatably contained in the valve chamber and cooperatively engaged with the valve housing for controlling a flow of exhaust gas; a transmission member rotationally driving at least one valve shaft of the valve body; and a plurality of bearing bushings mounted in the valve housing and rotatably supporting each valve shaft, wherein the valve body is coaxially arranged with an axial centerline of each valve shaft.
Since the valve body and the valve shaft have a coaxial cylindrical shape, it is possible to obtain good distribution of melt from a central portion of an end of the valve shaft at the time of casting, and to prevent thermal deformation from occurring due to partial material thickness. Accordingly, the external peripheral surfaces of the valve body and the valve shaft can be finished by cutting continuously after casting. Therefore, the valve body can be manufactured with high precision efficiently.
The high-precision valve body can have its external peripheral surface in thorough contact with the internal surface of the valve housing, so that it is possible to effectively restrain leakage of exhaust gas at the contact area and to carry out appropriate exhaust control. Further, since the cylindrical valve body has good weight balance about the axis line, it is possible to achieve a reduction of driving torque for the valve body and, hence, enhancement of response to the driving torque. Also, it is possible to minimize non-uniform loading on the bearing bushes, thereby contriving improved durability of the bearing bushes.
These and other aspects of the present invention are further accomplished by an exhaust control system for an internal combustion engine of a vehicle comprising a plurality of exhaust pipes from the internal combustion engine containing an exhaust gas flow, the exhaust pipes each having an intermediate portion; a common valve housing interposed in the intermediate portions of the exhaust pipes, the valve housing having at least one pair of inlet ports, at least one pair of outlet ports, and a valve chamber; a valve body having a cylindrical shape rotatably mounted within the valve chamber, and cooperatively engaged with the valve housing for controlling a flow of exhaust gas; a transmission member rotationally driving at least one valve shaft of the valve body; and a plurality of bearing bushings mounted in said valve housing and rotatably supporting each valve shaft, wherein the valve body is coaxially arranged with an axial centerline of each valve shaft.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.